Vapor compression refrigeration systems conventionally employ a condenser which receives a refrigerant in the vapor phase under relatively high pressure from a compressor. The condenser is operative to condense the refrigerant vapor to the liquid phase for ultimate transmittal to an evaporator whereat the refrigerant evaporates. Heat from the ambient is rejected to the refrigerant where it is absorbed as the latent heat of vaporization as the refrigerant evaporates. The now vaporized refrigerant is then directed to the compressor to be recycled through the system.
Conventionally such systems include a so-called receiver which is intended to receive liquid refrigerant from the condenser before it is transmitted to the evaporator. The primary purpose of the receiver is to assure that all refrigerant passed to an expansion device upstream of the evaporator is in the liquid phase. This means that the refrigerant quality is low and its enthalpy is also low to increase the evaporator's ability to absorb heat as the refrigerant evaporates. In this connection, the receiver acts as a reservoir for excess liquid refrigerant to assure that only liquid is fed to the expansion device in spite of system changes typically caused by the operation of the compressor. For example, in an automotive air conditioning system, the compressor is frequently stopped and started. Furthermore, when the engine to which the compressor is typically mechanically coupled is accelerating, compressor speed may also change, causing a change in the pressure at its inlet which in turn affects the flow rate of refrigerant in the system.
It is desirable to integrate the receiver with the condenser in many instances. For example, in so-called parallel flow condensers of the multipass type, integration of the receiver with the condenser assures that only liquid refrigerant will be fed to the last pass of the condenser which then acts solely as a subcooling pass. When such is accomplished, the increased subcooling further lowers the refrigerant quality while reducing the enthalpy of the refrigerant delivered to the evaporator to achieve the efficiencies mentioned earlier. Moreover, integration of the receiver with the condenser eliminates the need for a separate receiver/dryer elsewhere in the system and has the ability to reduce the total cost of the system as well as the quantity of refrigerant that must be charged into the system.
In this latter respect, it is well known that certain refrigerants are not environmentally friendly. For example, CFC 12 is thought to degrade the protection ozone layer surrounding the earth. Other refrigerants such as HFC 134a, while less damaging of the ozone layer, are thought to contribute to the so-called greenhouse effect which may be responsible for global warming. Because in automotive air conditioning systems, the compressor is driven by the vehicle engine, it cannot be hermetically sealed as in residential or commercial air conditioning units. As a consequence, there is the potential for escape of the refrigerant through compressor seals with the resulting deleterious effects on the environment. Thus, refrigerant charge volume is of substantial concern.
It is also known for receivers to be provided with means for filtering and/or drying the refrigerant to assure its purity, thereby avoiding inefficient operation. When such means for filtering and/or drying are provided in an integrated condenser/receiver, it is often desirable to service the receiver one or more times during the useable life of the condenser by replacing, replenishing, or refurbishing the means for filtering and/or drying. Thus, it is desirable to construct the receiver so that the means for filtering and/or drying can be selectively inserted into and removed from the receiver one or more times during the useable life of the condenser.
U.S. Pat. No. 5,934,102 issued to DeKeuster et al. discloses one exemplary example of a known integral condenser/receiver that allows for periodic servicing of the receiver. Specifically, DeKeuster et al. discloses a receiver (22) that is closed by a threaded cap (62). The cap (62) is removable and allows for a filter and/or a conventional drying material or desiccant to be introduced into the receiver (22). Other known integral receiver/condensers also included threaded plugs or caps that allow such servicing of the receiver. While many of these known constructions are acceptable for their purpose, there is always room for improvement.